(Photo: Richard Newstead)

Gardeners who thought they were giving a helpful boost to their local bee populations by planting “bee friendly” gardens may in fact be doing more harm than good, according to a new study released today.

Environmental groups Friends of the Earth-US and the Pesticide Research Institute tested a small sample of plants purchased from Lowe’s, Home Depot, and Orchard Supply Hardware (which is currently being acquired by Lowe’s), and found that just over half of the plants had been pre-treated with pesticides that they say are known to kill bees.

“The pilot study confirms that many of the plants sold in nurseries and garden stores across the U.S. have been pre-treated with systemic neonicotinoid insecticides, making them potentially toxic to pollinators,” said Timothy Brown, co-author of the study and associate scientist with the Pesticide Research Institute.

Thirteen samples were purchased in the San Francisco Bay area, the Washington, D.C. area and in Minneapolis, and were made up of soft-stemmed flowering plants known to attract both bees and pest insects like aphids. The plants included squash, tomato, pumpkin, zinnia, daisy, salvia and gaillardia.

Of the samples tested, the tomato plant purchased in California had the highest concentration of pesticide.

Stephen Holmes, a spokesperson with Home Depot, says they haven’t yet reviewed the study. “But the importance of the bee population is something we take very seriously, so we’ll be reaching out to the study groups to learn more.”

Lowe’s did not respond to our request for an interview.

Bayer Crop Science said in an email that they have not seen the report, and cannot comment on its scientific merit, “except to say that extensive research has shown that neonicotinoids are not responsible for honey bee colony decline.”

“The fact that residues of a registered product were allegedly found in some ornamental plants does not mean that honey bees were exposed to them, nor does it indicate causation for colony decline, which most experts attribute to a number of factors, including parasites, diseases, nutritional deficiencies, beekeeping practices and loss of habitat,” adds Bayer spokesperson Becca Hogan.

It’s a stance the company also took when they launched a controversial “bee tour” last spring, and on its “Bee Care” website, which claims that bee losses are not a new phenomenon, and that the “overall number of honey bee colonies worldwide has increased by some 45 percent over the last 50 years, not decreased.”

The European Union disagrees, and is expected to suspend the use of three neonic pesticides later this year, after an earlier study identified risks to bees exposed to the insecticides.

There’s plenty of skeptisism here at home too. Last month lawmakers introduced the Save America’s Pollinators Act, which would direct the EPA to “suspend use of the most bee-toxic neonicotinoids for use in seed treatment, soil application, or foliar treatment on bee attractive plants within 180 days, and to review these neonicotinoids and make a new determination about their proper application and safe use.”

Why is this class of pesticides getting such scrutiny?

As we told you earlier this spring, unlike older pesticides, neonicotinoids are typically applied to seeds before planting crops like corn and soybeans. It’s then taken up through the vascular system of the plant and expressed through the pollen and nectar, which bees rely on for food. (Bees aren’t the only worry. There are also serious concerns that neonicotinoids are harming birds and aquatic life as well.)

According to Paul Towers, spokesperson for the Pesticide Action Network, the introduction of neonicotinoids onto farms in the mid-2000s coincides with more widespread bee-colony collapses than had been seen before. The group has filed a lawsuit with the Environmental Protection Agency to curb the widespread use of the pesticide.

The new study comes with plenty of recommendations for keeping bees safe, aimed at everyone from garden retailers to municipalities to consumers. They include stopping the use of all neonicotinoids on landscaping plants, and a call for stores to stop offering pesticides like Merit or Meridian on store shelves.

“This is just a snapshot of how the pesticides are being used in home garden plants,” says Brown. “But I think it’s a really important study for people to be aware of when they plan out their gardens next season, and we hope the retailers will take some action on this.”

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